Retrieval of a wind profile from the Galileo Probe telemetry signal

The Galileo Probe Doppler Wind Experiment: Measurement of the deep zonal winds on Jupiter

“…Also shown are the retrieved winds when the probe descent longitude is in error by the 99% amount of 0.19 ø (dot-dashed curve). It is seen that, under the worst case assumptions of no thermal corrections for the USO stability, descent velocity errors of 5%, and the 99% Notes: 1, Constant effect (which is completely removable from the Doppler profile) and uncertainty; uncertainty is due to uncertainties in probe and orbiter radial locations, and in GMj; 2, based on Orton III atmosphere, refractive properties of H2, He, NH3, and CH4, probe aspect angle of 10 ø at 20 bars depth; uncertainty in NH 3 mixing ratio of 10%, and 0.1% uncertainty in helium and hydrogen mixing ratios assumed [Atkinson and Spilker, 1991;Pollack et al, 1992]; 3, assuming model ionosphere of constant electron density equal to 5 x 10 4 cm -3 over a 4000 km layer; a better model would be that of Hinson et al [1997], however, the basic conclusion that the ionospheric effect is negligible remains unchanged; 4, assuming probe spin rate of 30 rpm and probe aspect angle of 5 ø [Atkinson, 1989]; 5, assuming probe spin rate of 30 rpm [Atkinson, 1989]…”

“…Since nearly all the solar energy is absorbed by methane in the lower stratosphere (1-100 mbar), in the ammonia clouds (bottom level at ---700 mbar), and absorbed and scattered by aerosols and other gasses at slightly deeper levels [Hunten et al, 1980], no significant global-scale circulation is expected to result from solar insolation. A wind profile driven principally by differential solar heating would therefore be expected to diminish rapidly in the upper 2 bars of the atmosphere [Pollack et al, 1992].…”

“…For most of the tests the dose rates were between 0.5 and 3.0 rad/s. As discussed in detail by Atkinson [1989] and summarized by Pollack et al [1992], a model was developed based on the test results that reproduces the gross characteristics of the use radiationinduced frequency drifts. On the basis of the test results and the empirical model developed byAtkinson [1989], the nominal radiation-induced 30 min fractional frequency drift rate is expected to be less than -1 x 10 -'•, decreasing to -0.2 x 10 -9 by the end of the descent mission.…”

“…A number of other sources of error potentially damaging to the accuracy of the wind retrieval have been considered and documented in detail by Atkinson [1989] and summarized by Pollack et al [1992]. Among these are digitization errors (from the finite frequency word length in the orbiter receiver buffer), gravitational redshift, probe antenna/spin axis misalignment and antenna polarization/probe spin coupling, second-order Taylor, Doppler, and special relativistic effects, and atmospheric [Atkinson and Spilker, 1991] and ionospheric refraction effects.…”

Refraction effects on the Galileo probe telemetry carrier frequency

“…Paper number 90RS02529. 0048-6604/91/90RS-02529508.00 31 A vertical profile of zonal winds at the probe location can be retrieved from the time history of the RRL carrier frequency (see Atkinson [1989] or Pollack et al [1990]). From accurate reconstructions of spacecraft trajectories a frequency profile is computed.…”